arachnoid villi


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Related to arachnoid villi: hydrocephalus, choroid plexus

villus

 [vil´us] (L.)
a small vascular process or protrusion, as from the free surface of a membrane.
arachnoid villi microscopic projections of the arachnoid into some of the venous sinuses.
chorionic villi see chorionic villi.
intestinal villi multitudinous threadlike projections covering the surface of the mucous membrane lining the small intestine, serving as the sites of absorption of fluids and nutrients.
synovial villi slender projections from the surface of the synovial membrane into the cavity of a joint; called also haversian glands.

a·rach·noid vil·li

tufted prolongations of pia-arachnoid that protrude through the meningeal layer of the dura mater and have a thin limiting membrane; collections of arachnoid villus form arachnoid granulations that lie in venous lacunae at the margin of the superior sagittal sinus; the spongy tissues of the a. villus serve as one-way valves for the transfer of cerebrospinal fluid from the subarachnoid space to the venous system. Both a. villus and the granulations formed from them are major sites of fluid transfer.
See also: arachnoid granulations.

arachnoid villi

pl.
Etymology: Gk, arachne, spider, villus, shaggy hair
one of the many projections of fibrous tissue from the arachnoid membrane.

a·rach·noid vil·li

(ă-rak'noyd vil'ī)
Tufted prolongations of pia-arachnoid that protrude through the meningeal layer of the dura mater and have a thin limiting membrane; collections of arachnoid villi form arachnoid granulations that lie in venous lacunae at the margin of the superior sagittal sinus; the spongy tissue of the arachnoid villus contains tubules that serve as one-way valves for transfer of cerebrospinal fluid from the subarachnoid space to the venous system. Both arachnoid villi and the granulations formed from them are major sites of fluid transfer.
See also: arachnoid granulations
References in periodicals archive ?
Morphology of the arachnoid villi and granulations.
Drainage also occurs through the arachnoid villi in the sub-arachnoid space, flowing via blood and lymph into the lymphatics of the cranial nerves, the spinal nerves, inner ear and the cribiform plate of the ethmoid bone (forms the roof of the nasal cavity) (1).
Arachnoid villi are finger-like projections that help absorb CSF.
2-6) Kumar et al (2) postulated that these tumors arise from meningoepithelial cells, which are present throughout the arachnoid membrane with more concentration at the arachnoid villi within the dural venous sinuses.